This project serves to consolidate and to expand our efforts at identifying, localizing, and characterizing genes and gene products which are important in host pathogen relationships. While we have used colloidal gold and ferritin labeling to identify important cellular components which are located on the surface of various pathogens, new techniques of cryofixation, cryoultramicrotomy and immuno-labeling will allow precise localization of important antigens which may be located inside the cell. A broad range of molecular techniques will allow tracking of antigens through synthesis, processing and genetic control modulation. We have recently developed procedures for laboratory synthesis of uniform, precisely-sized colloidal gold markers which, when coupled with functional and specific antibody molecules, will allow for multiple antigen location and subsequent ultrastructural analysis.